Mission: Critical (Validity, Truth, Soundness)

Validity, Truth, and Soundness

Validity

Truth

Burden of Proof

Soundess

The first rule in evaluating any argument is never bother to disagree with a conclusion, because if you find nothing wrong with its form (or how the argument is made) and nothing wrong with its content (or the assumptions on which the argument is based), then you must accept its conclusion. As a result, to challenge an argument, you must challenge either its form or its content, not its conclusion directly. Because we can always evaluate the form of an argument, but not always its content, the process of analyzing an argument usually begins with its form.

Validity. When the form of an argument is acceptable, that is, when its premises and conclusion are in the proper relationship, we say that the argument is valid. A valid argument, then, is one that is in an acceptable form; and invalid argument is one in an unacceptable form. Rules for determining the validity of an argument are given in the sections on inductive and deductive reasoning. If an argument is found to be invalid, all judgment of its must be suspended because, to be acceptable, an argument must be valid. The conclusion of an invalid argument is not necessarily wrong; because of the invalidity, there is simply no way to evaluate that argument.

Truth. If, however, the form of an argument is found to be valid, then the content of its premises must be evaluated, to determine if they are true or false. A true premise is one that you believe has or can be verified, or is self-evident, in the case of a verifiable statement, or has or can be justified, or is self-evident, in the case of an evaluative or advocatory statement. The verification or justification usually comes in the form of support, such as evidence, expert opinion, and supporting arguments.

As a general rule, in judging premises and their support, you should accept as verifiable or justifiable all claims that follow these three rules:

They are not in conflict with what you know or understand to be true.
They do not require you to believe or accept other unsupported elements that are in conflict with what you know or understand to be true.
They bear the proper burden of proof.

Burden of Proof refers to the sense you have, in any dispute, of how much each side needs to prove in order to win your agreement. Sometimes, this burden of proof is an established rule: in the United States, for example, the criminal court system operates on the rule that a person is innocent until proven guilty, which means that the prosecution carries all of the burden of proof; if the defendant is not proven guilty, then he or she should not be convicted of a crime, even if the defense cannot or does not prove him or her innocent of that crime.

Generally, by initiating a claim one takes on a greater degree of the burden of proof than the same position would warrant otherwise. If, for example, Warren said, "California became a state in 1850," he would be expected to offer more proof for his position than if someone else said "California became a state in 1851," and Warren disagreed. In an easily verifiable case like that, the burden of proof is almost even, so the person making the claim is usually expected to support it first.

In most arguments, however, it is usually the side that supports altering or rejecting the status quo--the current beliefs, practices, and information--which has most of the burden of proof. The more controversial the matter, generally speaking, the more evenly is the burden of proof shared by all sides; and the more extreme or unusual one side of an argument is, the greater its burden of proof. In such extreme cases, initiating the claim is normally insufficient to offset the burden of proof. Thus, if Aziza says, "I don't believe in ghosts," we might be willing to accept her claim without any support, even though she has initiated it, because the burden of such an argument would be carried overwhelmingly by the side that supports a belief in ghosts.

Intentionally shifting the burden of proof, in order to avoid offering support for one's premises, is a logical fallacy.

Consider the following arguments:

I can prove there is life on Mars. Samples of Martian rocks show evidence of the kind of chemical reaction that can only involve a living organism.
I can prove there is life on Mars. Spectroscopic analysis through the Hubble telescope has revealed a purplish area on the Martian surface, and according to Mozyritzski's Second Law, that purplish area must be associated with living organisms.
I can prove there is life on Mars. A spaceship filled with Martians abducted me last night.
Prove there is life on Mars? Can you prove there isn't?

The fourth one is the easiest to deal with: at the minimum, a claim of life on Mars carries some of the burden of proof, and therefore has to be substantiated. The fact an opponent cannot disprove the claim is insufficient for the claim to be accepted; it must be proved. The third argument makes the same claim and does support it, but the support (that the speaker was abducted by Martians) requires you to believe something else that is itself unsupported and even more unusual. The second argument is similar to the third, although it may be easier to accept Mozyritzski's Second Law (whatever that is) than Martian abductors; we can reject Martian abductors without further consideration, but to accept or reject an argument based on Mozyritzski's Second Law, we first need to find out what it is, whether it applies in this case, and how accepted it is generally. The first argument was, in fact, made by scientists in 1996, and it is certainly the most creditable of the four examples here. That "chemical reaction" may be no more verifiable than Mozyritzski's Second Law, but it is more accessible. (In fact, other scientists soon disupted the claim.) So, as presented above and without further support, those four arguments appear in descending order of their acceptibility. Yet even the claim, "There's no life on Mars," would carry some of the burden of proof, if for no other reason than someone initiated it.

Soundness. Finally, if an argument is valid and its premises are true, it is termed a sound argument, and its conclusion must be accepted. In many cases, however, there is insufficient reason to find the premises of a valid argument totally true; the more complex the argument, the less likely that it will be considered undeniably sound. In such cases, we often talk of the "relative soundness" of an argument by describing it as strong or weak. A strong argument is valid in form, and with premises and support that make a compelling case for its acceptance. A weak argument is also valid in form, but its premises and support do not compell their acceptance.

Exercises:

1. In a valid argument . . .

the conclusion must be accepted.: the premises are true.
the form is acceptable.: the burden of proof is carried.

2. "Strong" and "weak" are terms that measure what about an argument?

validity: truth
soundness: burden of proof

3. The best way to begin evaluating an argument is usually on its . . .

validity: truth
soundness: burden of proof

4. How controversial an argument is can affect its . . .

validity: truth
soundness: burden of proof

1. In a valid argument . . .

You answered:

the conclusion must be accepted.

The conclusion must be accepted in a sound argument, because there the form is valid and the premises are true. Since the premises are not necessarily true in a valid argument, there is insufficient reason to accept its conclusion.

1. In a valid argument . . .

You answered:

the premises are true.

Validity has nothing to do with the truth of the premises, but with the way those premises are related to the conclusion.

1. In a valid argument . . .

You answered:

the form is acceptable.

Correct!

Validity is only a measure of form, not content.

1. In a valid argument . . .

You answered:

the burden of proof is carried.

Burden of proof is connected with establishing the truth of the premises, and has nothing to do with the validity of an argument.

2. "Strong" and "weak" are terms that measure what about an argument? You answered:

validity

Validity has to do with the form of an argument, and the form is either an unqualified valid or invalid.

2. "Strong" and "weak" are terms that measure what about an argument? You answered:

truth

Premises are either true, false, or of unknown value, and so are not described by themselves as "strong" or "weak." Those terms are usually reserved for the description of how the premises support the conclusion.

2. "Strong" and "weak" are terms that measure what about an argument? You answered:

soundness

Correct!

In cases where a valid argument's premises cannot be entirely accepted as true or rejected as false, the soundness of an argument is described in terms of "strong" or "weak."

2. "Strong" and "weak" are terms that measure what about of an argument? You answered:

burden of proof

While the burden of proof can be greater or weaker depending on the argument, that variation is not normally described in terms of "strong" and "weak."

3. The best way to begin evaluating an argument is usually on its . . .

You answered:

validity

Correct!

The reason to begin evaluating an argument by looking at its validity is simple: all arguments are either valid or invalid, and there's no point in continuing to analyze an invalid one.

3. The best way to begin evaluating an argument is usually on its . . .

You answered:

truth

The truth of the premises is important in determining the soundness of an argument, but there is an earlier step which may eliminate the need to establish truth or soundness.

3. The best way to begin evaluating an argument is usually on its . . .

You answered:

soundness.

Evaluating soundness is the last step in judging an argument, not the first.

3. The best way to begin evaluating an argument is usually on its . . .

You answered:

burden of proof.

The burden of proof needs to be established before any judgment is made on an argument's soundness, but evaluating soundness is the last step in judging an argument, not the first.

4. How controversial an argument is can affect its . . .

You answered:

truth

While controversy might make you look more closely at the support offered for a premise, it should not directly affect your determination of the truth or falseness of that premise.

4. How controversial an argument is can affect its . . .

You answered:

soundness

Soundness is determined by the validity of the argument and the truth of its premises, and controversy should have no effect on either validity or truth.

4. How controversial an argument is can affect its . . .

You answered:

burden of proof

Correct!

The more controversial a subject, the more support there is for both sides, and therefore the more evenly the burden of proof is divided. This does not mean, incidentally, that in a controversy both sides have roughly equal support; it only means that more support has been offered by both sides than there might have been without the controversy, and even a general awareness of the support offered by both sides will mean an insistence that they both will carry a great burden of proof. Note, therefore, that the burden of proof is not always a static quantity, that is simply divided up differently between the sides, depending on the argument involved; instead, the burden as a whole in controversial arguments, meaning that both sides are often required to carry a heavier burden of proof, even though their proportions of the burden may remain roughly the same.

4. How controversial an argument is can affect its . . .

You answered:

validity

Validity is strictly a matter of the form of the argument; it remains the same, in theory, even when the argument's claims make no literal sense at all. Therefore, the controversial content of an argument should not affect the validity of its form at all.

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